removes duplicate lines like UNIX uniq without having to sort the lines first, and preserves the line positions keeping the first match in the list.

#!/usr/bin/perl

while (<>) {
    next if (defined $list{$_});
    $list{lc($_)} = [ $i++, $_ ];
}

print map { $_->[1] }
      sort { $a->[0] <=> $b->[0] } values %list;

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In reply to state preserving uniq by Chady

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